1. Field of the Invention
The present invention relates to a nozzle that discharges a processing liquid and a substrate processing apparatus including the same.
2. Description of the Background Art
Substrate processing apparatuses have been conventionally used to perform a variety of processes on substrates such as semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks or the like.
In a cleaning process of the substrate, for example, a cleaning liquid and a rinse liquid as a processing liquid is supplied in this order from a processing liquid supply nozzle supported on a tip of a nozzle arm that is arranged in a horizontal direction onto the substrate that is rotated.
As the cleaning liquid, chemical liquids such as buffered hydrofluoric acid (BHF), diluted hydrofluoric acid (DHF), hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, oxalic acid, ammonia water and the like are used.
In the substrate processing apparatus in which the chemical liquid is used as the processing liquid, a metal can not be used as a material for the processing liquid supply nozzle, the nozzle arm, a pipe and the like, since use of a metallic member causes metallic corrosion as well as metallic contamination caused by elution of metallic ions. Therefore, the processing liquid supply nozzle, the nozzle arm, the pipe and the like are formed of a resin material such as fluororesin and the like having superior chemical resistance.
In a substrate processing apparatus of JP2002-170803 A, for example, a pipe through which a chemical liquid flows is connected between a downstream portion of a chemical liquid mixer and an upstream portion of a processing liquid supply nozzle and the pipe is formed of a tube made of fluororesin having superior chemical resistance.
Since the resin material such as the fluororesin or the like is an insulating material, however, when the processing liquid flows through the inside of the processing liquid supply nozzle, a friction between the processing liquid and an inner surface of the processing liquid supply nozzle causes static electricity, and consequently the processing liquid becomes charged.
When the processing liquid with a large amount of charges (an absolute value of the electric potential of charges) is supplied onto the substrate to be an processing target, a spark is generated by electric discharge from the processing liquid to the substrate at the moment of the supply of the processing liquid, so that circuits and devices formed on the substrate are damaged in some cases.
Moreover, the nozzle arm requires strength in order to stably support the processing liquid supply nozzle, since the nozzle arm horizontally extends from a position outside the substrate to above the center of the substrate. In a case where the nozzle arm is formed of resin as mentioned above, it is necessary to make the nozzle arm have a larger radial thickness in order to ensure strength.
Thus, the weight of the nozzle arm increases as the outer diameter thereof becomes larger. This causes a load applied to a drive system of the nozzle arm to be larger. In addition, the surface area of the nozzle arm becomes larger, so that the amount of the scattered processing liquid adhering to the nozzle arm also increases.
If the processing liquid adhering to the nozzle arm drops on the substrate, it becomes a cause of processing defects. Furthermore, if the processing liquid adhering to the nozzle arm is dried, it becomes particles, which adhere to the substrate in some cases.
Moreover, when the processing liquid is vibrated by reaction, the nozzle arm and the processing liquid supply nozzle are vibrated accordingly, since the nozzle arm formed of resin has flexibility. In addition, the processing liquid supply nozzle is likely to be vibrated because of the force generated when the discharge of the processing liquid from the processing liquid supply nozzle is started. Thus, the processing liquid is supplied onto irregular positions on the substrate with an irregular force at an irregular rate, so that processing defects of the substrate are liable to occur.